Table 3.

Leaf photosynthetic parameters estimated for leaves at upper, middle and lower level of the plant

Treatment	PAR R:FR	High High	High Low	Medium High	Medium Low
A max (μmol m−2 s−1)
Upper leaf		16.1 ± 1.5 a	17.2 ± 2.2 a	11.7 ± 1.2 b	12.2 ± 0.6 b
Middle leaf		14.0 ± 2.3 a	16.1 ± 2.4 a	10.8 ± 1.7 b	10.0 ± 1.2 b
Lower leaf		10.7 ± 2.2 a	10.0 ± 1.0 ab	7.9 ± 1.1 b	8.2 ± 1.5 ab
R d (μmol m−2 s−1)
Upper leaf		0.85 ± 0.39 a	0.83 ± 0.39 a	0.25 ± 0.08 b	0.48 ± 0.17 ab
Middle leaf		0.53 ± 0.38 a	0.77 ± 0.28 a	0.50 ± 0.43 a	0.25 ± 0.18 a
Lower leaf		0.45 ± 0.18 a	0.35 ± 0.18 a	0.19 ± 0.33 a	0.28 ± 0.08 a
Φ CO2LL(inc) (mol CO2 mol−1 photon)
Upper leaf		0.051 ± 0.006 a	0.053 ± 0.010 a	0.046 ± 0.006 a	0.048 ± 0.003 a
Middle leaf		0.052 ± 0.007 a	0.056 ± 0.007 a	0.053 ± 0.005 a	0.052 ± 0.009 a
Lower leaf		0.048 ± 0.007 a	0.047 ± 0.007 a	0.041 ± 0.008 a	0.045 ± 0.005 a
θ
Upper leaf		0.70 ± 0.05 a	0.47 ± 0.21 b	0.70 ± 0.05 a	0.59 ± 0.01 ab
Middle leaf		0.71 ± 0.07 ab	0.56 ± 0.1 c	0.76 ± 0.04 a	0.61 ± 0.09 bc
Lower leaf		0.71 ± 0.06 a	0.46 ± 0.11 b	0.72 ± 0.07 a	0.58 ± 0.13 ab
Slope s		0.05 ± 0.01 a	0.05 ± 0.01 a	0.03 ± 0.01 b	0.03 ± 0.01 b
Coefficient k		0.12 ± 0.02 b	0.15 ± 0.03 ab	0.13 ± 0.03 ab	0.19 ± 0.04 a

A _max is the maximum leaf photosynthetic rate at saturating incident light. R_d is the dark respiration rate. Φ_CO2LL(inc) is the quantum yield of CO₂ assimilation on the basis of incident light. θ is the curvature factor of the light response curve. s is the slope of the linear regression between A_max and R_d. k is the coefficient describing the relationship between light gradient and A_max gradient in the canopy. Values of A_max, R_d, Φ_CO2LL(inc) and θ are mean ± s.d. from four statistical replicates, each of which includes two plants. Values of s and k are estimate ± error of estimation. Letters following the numbers in each row indicate significant differences when comparing between treatments (P < 0.05).